Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$235.58	11.146%	$261.8377	$261.84	$261.85	$261.80
Purchase #2	$215.79	4.484%	$225.466	$225.47	$225.45	$225.50
Purchase #3	$249.78	11.235%	$277.8428	$277.84	$277.85	$277.80
Purchase #4	$146.67	8.740%	$159.489	$159.49	$159.50	$159.50
Purchase #5	$164.39	4.772%	$172.2347	$172.23	$172.25	$172.20
Purchase #6	$246.81	13.682%	$280.5785	$280.58	$280.60	$280.60
Purchase #7	$76.53	7.865%	$82.5491	$82.55	$82.55	$82.50
7 purchase totals =	$1,335.55		$1,459.9978	$1,460.00	$1,460.05	$1,459.90